DRIVEABILITY AND EMISSIONS 6E1-63
FUEL METERING SYSTEM CHECK
Some failures of the fuel metering system will result
in an “Engine Cranks But Will Not Run” symptom. If
this condition exists, refer to the Cranks But Will Not
Run chart. This chart will determine if the problem is
caused by the ignition system, the ECM, or the fuel
pump electrical circuit.
Refer to Fuel System Electrical Test for the fuel
system wiring schematic.
If there is a fuel delivery problem, refer to Fuel System
Diagnosis, which diagnoses the fuel injectors, the fuel
pressure regulator, and the fuel pump.
Followings are applicable to the vehicles with
closed Loop System:
If a malfunction occurs in the fuel metering system, it
usually results in either a rich HO2S signal or a lean
HO2S signal. This condition is indicated by the HO2S
voltage, which causes the ECM to change the fuel
calculation (fuel injector pulse width) based on the
HO2S reading. Changes made to the fuel calculation
will be indicated by a change in the long term fuel trim
values which can be monitored with a Scan Tool. Ideal
long term fuel trim values are around 0%; for a lean
HO2S signal, the ECM will add fuel, resulting in a fuel
trim value above 0%. Some variations in fuel trim
values are normal because all engines are not exactly
the same. If the evaporative emission canister purge is
02 status may be rich condition. 02 status indicates the
lean condition, refer to DTC44 for items which can
cause a lean HO2S signal.
FUEL INJECTOR COIL TEST
PROCEDURE AND FUEL INJECTOR
BALANCE TEST PROCEDURE
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart:
2. Relieve the fuel pressure by connecting 5-8840-
0378-0 T-Joint to the fuel pressure connection on
the fuel rail.
Caution: In order to reduce the risk of fire and
personal injury, wrap a shop towel around the
fuel pressure connection. The towel will
absorb any fuel leakage that occurs during
the connection of the fuel pressure gauge.
Place the towel in an approved container
when the connection of the fuel pressure
gauge is complete.
Place the fuel pressure gauge bleed hose in an
approved gasoline container.
With the ignition switch OFF open the valve on the
fuel pressure gauge.
3. Record the lowest voltage displayed by the DVM
after the first second of the test. (During the first
second, voltage displayed by the DVM may be
inaccurate due to the initial current surge.)
Injector Specifications:
Resistance Ohms
Voltage Specification at
10°C-35°C (50°F-95°F)
11.8-12.6 5.7-6.6
• The voltage displayed by the DVM should be
within the specified range.
• The voltage displayed by the DVM may
increase throughout the test as the fuel injector
windings warm and the resistance of the fuel
injector windings changes.
• An erratic voltage reading (large fluctuations in
voltage that do not stabilize) indicates an
intermittent connection within the fuel injector.
5. Injector Specifications:
Highest Acceptable Voltage
Reading Above/Below
35°C/10°C (95°F/50°F)
Acceptable
Subtracted
Value
9.5Volts 0.6Volt
7. The Fuel Injector Balance Test portion of this
chart (Step 7 through Step 11) checks the
mechanical (fuel delivery) portion of the fuel
injector. An engine cooldown period of 10 minutes
is necessary in order to avoid irregular fuel
pressure readings due to “Hot Soak” fuel boiling.
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